Unknown field Phone

Need help from any "Jimmies", ex-Jimmies or people in the know about telephones. My friend pick up this field phone at a local antique shop in Summerside. Not sure if it's military or not, paint that remains is O.D. with tan web strap. It's 5" deep by 7" wide by 9 1/2" high. Apologies for the photos, I just got my first digital camera and I'm still learning the ins and outs.

Thanks guys. Appreciate the quick response. Any idea of time frame? I'm thinking late 40's-early 50's because of what looks like a hand written depot repair log on the inside cover. Any more infor from you or anyone else is much appreciated.